Fixed-ratio escape reinforcement.

Escape responses of squirrel monkeys were reinforced according to a fixed-ratio schedule. The reinforcement was a period of safety from a stimulus that signalled the delivery of intermittent pain-shocks. When the frequency of shock was gradually reduced, the performance remained at a high level until the shocks were quite infrequent. Similarly, the duration of the period of safety could be reduced to a few seconds with little loss of behavior. Thus, the responses appeared to be reinforced by even a brief period of safety, the actual degree of shock reduction being fairly slight. The changes in responding during this fixed-ratio escape procedure were comparable to the response changes typically obtained during fixed-ratio food procedures.